The inventive concepts described herein relate to binary image sensors and unit pixels of binary image sensors.
An image sensor is a device which can convert an optical image into an electrical signal. As computer and communications industries develop, demand for image sensors having improved performance may increase in various fields such as digital cameras, camcorders, PCS (Personal Communication Systems), game machines, security cameras, medical micro cameras, robots, and so on.
A charge coupled device (CCD) image sensor and/or a CMOS image sensor may be used as an image sensor. The CMOS image sensor may be characterized in that a driving manner is simpler and a signal processing circuit is integrated in a single chip for downsizing. Since power consumption of the CMOS image sensor is relatively low, the CMOS image sensor may be more easily applied to products with a limited battery capacity. Also, the CMOS image sensor may be fabricated using a CMOS process technology, so that fabrication costs may be reduced.
The CMOS image sensor or the CCD image sensor may be formed of a plurality of pixels constituting or made up of unit pixels. A size of a pixel may be about 2 micrometers (μm). In the event that a pixel is fabricated to have a size less than 1 μm, it may be difficult to achieve performance improvement of the image sensor, for example, due to a narrower dynamic range, a smaller full well capacity, and/or a signal to noise ratio (SNR) of less than about 10 to 20:1.